Gennady Badin modern technologies of construction and reconstruction of buildings. Steel tubular piles, open at the bottom

2015-03-17 09:41:38 12130

The crop production industry, which is one of the main links in agricultural production, has recently experienced significant economic pressure stemming from rising energy prices.

This, in turn, leads to the need to search for new technologies that would, to a certain extent, compensate for the increasing financial costs of fuels and lubricants, energy products, agricultural machinery and technological materials.

Fig.1. Top Down TD 400 cultivator in operation

In this regard, one of the world's leading manufacturers of agricultural, including soil-cultivating, equipment, Väderstad-Verken AB (Sweden), is acting accordingly. Without entering into the discussion “to plow or not to plow,” she solves in her own way the strategic question of what a machine should be like in order to harmoniously fit into any crop rotation, reliably and efficiently carry out the technological process of cultivating the soil in a wide range of soil-meteorological conditions and technologies.

In 2009, UkrNIIPIT named after. L. Pogorely conducted field observations of the operation of the Top Down multi-purpose cultivator, models TD 400-900, manufactured by Väderstad-Verken AB. Observations were carried out on different farms, against different backgrounds. The main technical indicators of the cultivator models are given in Table 1.

Table 1. Main technical indicators of the cultivator
Indicator name	Indicator value
	Trailed
Aggregated, tractor power, kW
Operating speed, km/h
Construction working width, m
Cultivation depth, cm:
Surface cultivation
Pre-sowing cultivation
Cultivation with autumn plowing
Main cultivation
Number of service personnel, people.
Overall dimensions, mm
in working order:
in transport condition:
Track, mm
Transport clearance, mm
Weight, kg
Specific gravity, kg/m
Number of disks, pcs.
Number of disks, pcs./m
Number of cultivator paws, pcs.
Number of cultivator paws, pcs./m

Technological features of the cultivator

Fig 2. Top Down TD 900 cultivator in operation

The technological scheme of this machine successfully combines advanced technological methods of soil cultivation and soil-cultivating working bodies that are already well-known and widely used in world practice. In this mechanism, this combination has a certain specificity: the disks in front guarantee the operation of the cultivator in any condition of the cultivated surface, in any conditions, even those saturated with exceptionally large volumes of plant residues, and the heavy roller at the rear determines the quality of the cultivated soil horizon. This may seem unnecessary, but this design guarantees high quality of the technological process, which is what the technological concept of the TopDown cultivator is designed for. During operation of the cultivator, four technological operations are simultaneously performed, namely:

• disking the soil surface while simultaneously crushing plant residues and mixing them with the surface layer of soil;
• loosening the soil with five types of replaceable cultivator tines to a depth of 5 to 30 cm, depending on the type of cultivation;
• leveling the loosened surface and additional crushing of lumps with rotating star-shaped disks;
• compaction of the loosened and leveled soil surface with ribbed rollers (rollers can be either steel or rubber).

First operation is performed by conical solid toothed discs (photo 4) with high cutting activity and wear resistance of the working part, for which the company is famous. Installed in echelon, in two rows in the front part of the cultivator, they ensure intensive cultivation of the surface layer of soil, mixing it with crushed plant residues. Each of the disks is attached to the beam individually using special clamps through rubber shock-absorbing elements, which ensure that the disks reliably follow the microrelief of the field, and also prevent destruction during collisions with stones or other foreign bodies that may be in the soil. The discs have bearings closed type and do not lubricate.

Under any conditions (uneven accumulation of plant residues on the field surface, low or high humidity and soil hardness), this group of working bodies processes and prepares the field surface for high-quality loosening of the root-containing soil layer.

Second operation is performed with chisel-type loosening paws (photo 5), arranged sequentially in four rows on the middle transverse bars of the cultivator frame. Each of the paws is hingedly attached to the transverse beam and is equipped with a hydraulic limiter of the resistance force acting on the paw, due to which, when hitting an obstacle (large stone, very compacted soil, etc.), the paw deflects back and up, avoiding damage. Depending on the working conditions and soil cultivation requirements, paws of different widths (50, 80, 120 mm) or a grip depth of 300 mm can be used.

Based on the chosen system of soil cultivation or the period of its implementation, as well as according to the put forward requirements, cultivator paws can carry out both local loosening of the soil with chisel-shaped tips to a depth of 1 to 30 cm, and continuous loosening with pointed paws. In this case, the root-containing horizon experiences a significant renewing effect.

Third operation is carried out by a leveler, which consists of a set of star-shaped disks (photo 6), installed relative to the surface of the earth in such a way that the lower lobes of the disks, interacting with the soil, set them into rotating motion, thereby achieving uniform transverse leveling of the loosened surface layer of soil. In any conditions, the field surface treated in this way will always have a profile aligned with the working width and in the direction of movement of the unit.

Fourth operation, the final one, is performed using ribbed compaction rollers (photo 6).

Each section of the roller is made up of separate hollow rings mounted on a common shaft with a rubber damper.

The shaft is mounted with its axles on bearing resistors. Both sections of rollers are installed frontally in one row behind the soil levelers. In order to prevent the accumulation of soil and plant residues, which can lead to disruption of the skating rink, scrapers are installed between the rings. Under the action of ribbed rollers, the surface layer of soil is compacted to an optimal state, a finely wavy surface is formed, in which atmospheric moisture can accumulate as completely as possible and an optimal aeration regime is maintained.

Due to this, favorable conditions are created for increasing the intensity of biochemical processes in the soil and the accumulation of nutrients in it. The company specifically recommends the use of a heavy metal roller in Ukraine. In Europe, rubber is often used on sandy soils.

Test results Each of the named groups of working bodies is equipped with hydraulic mechanisms for regulating their activity, allowing within a wide range to set the operating mode of the cultivator that will most fully meet the requirements of the next technological operation. This control system allows the operator to timely adjust the quality of the technological process and the functioning of one or another working body without leaving the workplace.

All cultivator models are well adapted to technical and technological maintenance and meet the requirements for transportation on general roads (except for the TD 900 model, the width of which in transport position is 5 m with an allowable width of 3 m).

The conditions for testing the Top Down TD 400 cultivator on stubble after harvesting spring barley in the 2009 season were quite difficult and not typical for the autumn period (humidity in the treated soil layer was in the range of 3.8-11.0% compared to standard 12- 27%, according to the initial requirements), but the results obtained further confirm the technological capabilities of the machine.

The performance quality of the Top Down TD 400 cultivator, equipped with chisel-shaped shares with wings, in combination with the Case ΙΙΙ 310 Magnum tractor was determined on three different speeds movement - 6, 9 and 12 km/h.

As a result of the agrotechnical assessment of the cultivator (Table 2), it was found that the quality of the main soil cultivation at three different speeds meets all agrotechnical requirements, even at low soil moisture levels. The number of lumps measuring 0-50 mm at a cultivation depth of 14.0-15.9 cm was 96.2-96.6% (according to agricultural requirements - no less than 80%). It should also be noted that the part of the embedded plant residues depends on the operating speed of the unit. When the speed increased from 6 km/h to 12 km/h, the portion of embedded plant residues increased from 36.9% to 63.1%.

During cultivation, plant residues of spring barley were mixed throughout the entire depth of the cultivated soil layer, but the vast majority of them were located at a depth of 0-12 cm.

The ridgedness of the field surface corresponded to the technological scheme of the cultivator.

The operational and technological performance indicators of the Top Down 400 cultivator were determined in conjunction with the CASE III 310 Magnum tractor (Table 2). The unit operated at speeds of 6, 9 and 12 km/h. Moreover, its productivity per hour of main time was 2.46 hectares, 3.57 hectares and 4.83 hectares, respectively.

Of course, for the stable execution of the technological process by the cultivator in the specified modes, the power source with which it is aggregated must have an engine power of 35-45 kW per meter of working width and corresponding traction characteristics.

During the testing period of the cultivator, no violations of the technological process were observed. In the time balance structure, with a standard shift duration, productive work time takes up 82%, 81% and 80%, and additional work time (for turning) - 2.9%, 4.0% and 5.4% according to the specified unit speeds .

The shift time utilization rate is 0.82, 0.81 and 0.80, which was influenced by the presence of auxiliary operations necessary for process continuity. Time spent on preparatory work and maintenance in the time balance structure takes up about 15%. Productivity per hour of shift time is 2.02 hectares, 2.89 hectares and 3.86 hectares, respectively. During the period of operation, no breakdowns of the unit were noted. The high performance characteristics of the machine combined with high technical reliability ensure that it can carry out significant annual volumes of work.

With a standard annual load of 200 hours and a cultivator service life of 8 years, operating costs are 0.26 man-hours/ha, direct operating costs are 293.26 UAH/ha.

The magnitude of direct operating costs associated with the operation of the TD 400 cultivator at different annual loads is shown in Fig. 8. It is obvious that an increase in annual load by 3 times, which is quite realistic, ensures a reduction in direct operating costs by almost 2 times. This allows us to focus on the amount of operating costs at the level of 150 UAH/ha.

High operational performance of the machine combined with high technical reliability ensures that it can carry out significant annual volumes of work.

The operational and technological performance indicators of the Top Down 900 cultivator, determined at a speed of 9.2 km/h in a unit with a CASE III 530 STEIGER tractor, also turned out to be quite high (Table 2). Its productivity per hour of main time is 8.06 hectares, per hour of shift and operating time - 6.37 hectares, it is directly proportional to the ratio of its working width to the working width of the TD 400 cultivator.

Efficiency calculation

The existing standard range of Top Down cultivator models, namely TD 300, TD 400, TD 500, TD 600, TD 700, TD 900, allows you to satisfy the needs of any farm, regardless of the size of land ownership and prevailing crop rotations. But this can be realized provided that the economy has the appropriate energy resources and highly qualified specialists.

Calculations of the efficiency of using the Top Down cultivator were carried out for its models TD 400, TD 700 and TD 900 in agricultural enterprises with grain legume specialization: winter rape, winter wheat, soybeans, corn, spring barley.

When calculating the load for the season by crop, the agrotechnical timing of soil cultivation, crops grown in crop rotation, production rates and the utilization rate of the studied cultivator models were taken into account.

The effectiveness of using mechanization tools largely depends on the organization economic activity. Therefore, when calculating the need for machines, the load during the peak period of their operation was taken into account. For timely cultivation of the soil, taking into account crop rotation and the size of the farm’s land (2500 hectares), each of the Top Down cultivator models (TD 400 - 1 pc., TD 700 - 1 pc., TD 900 - 1 pc.) will ensure soil cultivation within the established agricultural deadlines .

For a farm with agricultural land larger than 4500 hectares, 2 cultivators TD 400, TD 700 or 1 cultivator TD 900 are required.

For a farm of 6000 hectares, the need for Top Down cultivators is: TD 400 - 3 pcs., TD 70 0 - 2 pcs., TD 900 - 1 pc. From Fig. It is worth noting that the lowest direct operating costs on an area of ​​up to 2500 hectares will be provided by the use of a TD 400 cultivator, on an area from 2500 hectares to 4500 hectares - by a TD 700, and on an area from 4500 hectares to 6000 hectares - by a TD 900.

Table 2. Operational and technological indicators of the cultivator
Indicator name	Indicator value
Date 09/15/2009
Cultivator model
Travel speed, km/h
Cultivator working width, m
average cultivation depth, cm
standard deviation, cm
coefficient of variation, %
Quality of soil grinding, content of lumps by fraction, %
50.1-100.0 mm
More than 100.1 mm
Weed cutting, %
Covering of plant residues, %
Ridgeiness of the field surface, cm
Productivity, ha per hour:
Main
Replaceable
Operational
Operational and technological coefficients
Technological service
Process reliability
Using shift time
Use of operating time

Conclusions

Based on your Based on a thorough analysis of the design and the results obtained during field studies of the Top Down multi-purpose cultivator, the following conclusions can be drawn:

• the range of cultivators can satisfy the needs of agricultural enterprises regardless of the size of the crop area, harmoniously fitting into any crop rotation;
• Top Down cultivators have high technical and technological reliability and are easy to maintain;
• in combination with a properly selected tractor, they ensure high quality work in a wide range of soil and meteorological conditions and on different types and soil cultivation systems;
• The design of the cultivator provides for different options for equipping it with working parts, depending on soil conditions, agrotechnical background and the condition of the cultivated areas.

Thus, the conducted research confirms the effectiveness of the technological and layout concepts of the Top Down cultivator from Väderstad-Verken AB, which ensure the implementation of the entire complex of soil cultivation operations on farms using mulching and (or) conservation cultivation systems, as well as during moldboard cultivation in as steam and pre-sowing cultivators.

The creation of a model range of cultivators of different working widths, in the presence of power tools of the required power, makes it possible to effectively implement this concept in a farm of any size, regardless of the crop rotations and cultivation systems chosen by it, to sharply reduce the fleet of tillage machines and to maintain different technological strategies for different crops. In all cases, success will be guaranteed.

Find out more about Vaderstad technology:

The construction of buildings in the city is associated with many difficulties:

• cramped construction conditions,
• historical buildings in the area affected by the construction of the facility,
• large number communications under the building site,
• the customer’s desire to “squeeze out” the maximum of rentable space.

Under such conditions, constructing a building using an open method is simply not possible, and one of the safest and most effective ways out of the situation is the use of Top-down technology.

Top-down technology has found wide application in the construction of facilities in cramped urban areas, due to the gentle nature of the work. In addition, carrying out work using this technology makes it possible to significantly reduce construction time.

The essence of the method is the simultaneous construction of the underground and above-ground parts of the building.

Sequence of work using the Top-down method:

1. Construction of the structure for fastening the walls of the pit. The most preferred type of enclosing structure is the “wall in the ground”, due to its ability to prevent groundwater from entering the pit.
2. Construction of a pile foundation from ground level or from a pioneer pit. Most often, column piles are used, which serve as permanent supports for the floors of the underground part of the building. Piles can also be used as temporary supports.
3. Concreting of floor slabs, which act as spacer structures. Work on concreting the slabs is carried out as the soil is removed using small-sized equipment through the technological holes of the previously completed floor. In parallel, work can be carried out in the above-ground part of the building.
4. Construction of the foundation slab and construction of permanent load-bearing structures from bottom to top.
5. Dismantling of temporary support and spacer structures.
6. Technological holes are concreted in the slabs.

The use of Top-down technology requires participants in the construction process to strictly adhere to the sequence of work and comply with labor safety standards on site, since a large number of complex engineering solutions are used.

A similar construction method is semi top-down. Its main difference from top-down is that most excavation work is carried out in an open way, using excavators, and a much smaller amount of work is carried out under the protection of floors. In addition, the construction of the above-ground part is carried out only after completion of work in the underground part of the building.

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Method for constructing a pile foundation under heavy loads

Construction method pile foundation for heavy loads (Fig. 3.5) includes:

♦ immersion of the metal casing pipe, formation of the conductor by securing a system of removable horizontal and vertical centering hydraulic jacks on the metal casing pipe;

♦ formation of a well under the protection of a bentonite solution with penetration into slightly fractured limestones, replacement of a contaminated bentonite solution with a freshly prepared one, removing drill cuttings from the bottom of the well;

♦ formation of a pipe-reinforcement frame in the form of a connection of pipe and reinforcement parts, installation of an umbrella-limiter of the level of filling the well with concrete mixture approximately at the border of the transition of the reinforcement frame to the pipe;

♦ hanging the pipe-reinforcement frame above the conductor with the reinforcement part down, vertical centering and installation of the pipe-reinforcement frame in the well with eccentricity compensation and fixing the gaps from the walls and bottom of the well using the conductor;

♦ installation of a concrete pipe inside the frame and continuous concreting of the pipe-reinforcement frame and the wellbore from the bottom up under a high initial pressure of supplying the concrete mixture, with a decrease in pressure when the concrete mixture reaches the limiting umbrella;

♦ subsequent concreting with reduced pressure for supplying the concrete mixture and stopping the supply of the concrete mixture when the upper level of the pipe part of the pipe-reinforcement frame is reached;

♦ removing the concrete pipe from the well, filling the cavity between the conductor and the pipe part of the frame with coarse aggregate, temporarily holding the concrete monolith and dismantling the conductor.

Rice. 3.5. An example of a support, where well 1, pipe-reinforcement frame 2 with reinforcement part 3 and pipe part 4, level limiter 5 for filling the well with concrete mixture, conductor 6, concrete-cast pipe 7 are indicated

Top-down underground construction technology (Belgium)

During the construction of the Stockmann shopping center, for the first time in St. Petersburg, the advanced technology of top-down underground excavation was used, the essence of which is that a “wall in the ground” restrains water pressure and the underground floors do not grow “bottom up” from the bottom of the pit, but on the contrary, from the surface level “from top to bottom” to a depth of 15 m. Using the Belgian modern top-down technology, St. Petersburg engineers and builders acquired invaluable experience in underground construction, which turned out to be effective method. Monitoring the groundwater level during the work showed that its level did not change, and the pit was dry. Top-down– this is a buried structure, a rigid reinforced concrete structure around the perimeter, which allows to minimize ground settlement, which guarantees the safety of all buildings and structures located in the immediate vicinity of the work site, and there is also the possibility of using a “wall in the ground” as an enclosing wall, and the supporting structure.

The technology of work is as follows. The walls of the structure are erected in narrow and deep trenches, the excavated soil is replaced with bentonite solution. The solution creates hydrostatic pressure on the walls of the trench, keeping them from collapsing. Then a reinforcement frame is lowered into the dug trench, which is filled with high-quality concrete or reinforced concrete elements that displace the bentonite solution. This protects buildings located in close proximity to the construction site from settlement and deformation.

When using top-down technology, strong steel cores are inserted into the body of the pile, and the sheet pile is driven into the ground using a powerful imported vibrator.

Rice. 3.6. Examples of constructing a monolithic wall in the ground near existing buildings

Modern Western geotechnologies for fencing pits are adapted to the engineering and geological conditions of St. Petersburg. In Fig. Figure 3.6 shows examples of constructing a monolithic wall in the ground near existing buildings. The “wall in the ground” for the largest underground structure in the central part of St. Petersburg on the island of New Holland is shown in Fig. 3.7.

Rice. 3.7.“Wall in the ground”, on the island of New Holland

Rice. 3.8. Reconstruction of the Kamennoostrovsky Theater

During the reconstruction of the Kamennoostrovsky Theater (Fig. 3.8), work was carried out to restore the historical building and construct an underground space 6.5 m deep. This work is unique to world geotechnical practice (a restoration version of the top-down technology, when restoration goes up and underground construction goes down ).

In Kyiv, the Sky Towers at the Central Registry Office will rise 47 floors up and go down eight. For the first time in Kyiv, a building is being built from top to bottom - excavators are digging out the lower floors under the already built ones!

Foundations:

♦ barrett laying depth – up to 64.5 m;

♦ foundation slab depth – 28 m;

♦ thickness of the “wall in the ground” – 1.2 m;

♦ the depth of the “wall in the ground” is from 50.5 to 53.5 m.

Barretts– deep supports made in the ground. First, a well is drilled, then reinforcement is installed and concrete is poured. All this is done under pressure using drilling fluid (often bentonite). They are used in construction on soft soils (due to the great depth you can reach dense layers) and dense buildings (there are no vibrations, as when driving piles).

A “wall in the ground” is built similarly to barrets - drilling, installing reinforcement and concreting.

Tower construction technology:

♦ A “wall in the ground” is being constructed along the perimeter of the construction site.

♦ The foundation drilled injection piles - barrettes - are poured.

♦ A pit is dug up to a certain level - for example, “-1” floor. At the bottom of the pit, an interfloor floor is poured, as well as a floor on the level above - they perform the function of two-tier “walls in the ground” struts. Technological openings are left in the ceilings.

♦ Excavators select soil first in the areas of technological openings, and then under the floors of the floor located above.

♦ When the excavators have selected the soil for the entire volume of the floor, the next floors are poured and the process is repeated until the builders reach the lowest level according to the project. When all the soil has been selected and the floors have been poured, technological openings (elevator shafts or parking ramps) are traditionally poured from bottom to top.

In combination with barrettes and a “wall in the ground”, this method allows you to preserve the surrounding buildings. This will be the first building in Kyiv higher than 200 m, built in difficult geological conditions, which required deep and unique foundations using top-down technology.

Driving sheet piles

This technology uses welded steel sheet piles from elements of a semicircular profile “F-profile piles”.

The semicircular pile profile is the most economical form of sheet piles in comparison with traditional trough and T piles. Savings are achieved both by reducing the metal used and by reducing labor costs when installing piles.

At the same time, piles made from semicircular profile elements have a number of advantages. They are able to withstand heavy loads, their moment of resistance is up to 12,000 cm 3 per linear meter of wall. F6012 piles with a moment of resistance of 6000 cm 3 per linear meter of wall were used in the construction of a multifunctional complex near the Moskovsky railway station in St. Petersburg, which made it possible to abandon the “wall in the ground” and the excavation of a pit using top-down technology and carry out open-pit excavation.

The width of panels made from F-profile piles can reach 2 m, which entails a reduction in immersion cycles. The equipment does not require modernization - when vibrating, standard clamps for a trough-shaped profile are used, and when driving piles using the impact method, simple caps are used.

Due to lower metal consumption, reduction of driving cycles due to an increase in the width of the profile, due to its high turnover, i.e., the possibility of reuse, savings can be 25–35% compared to the use of conventional sheet piles.

Welded piles and panels made from semicircular profile elements are widely used in dense urban areas for pits up to 10 m deep without bracing and up to 24 m deep with bracing or anchoring. Sheet pile locks designed by Beregstal PA, having good soil and water resistance, provide reliable waterproofing of pits during the construction of foundations.

Innovative solutions for pile foundation construction

With the participation of the Russian Academy of Engineering, a set of equipment for pile foundation construction has been developed, providing full-scale technical equipment latest technologies pile foundation construction.

The complex includes a set of a model range of shockless driving injection devices for the production of reinforced concrete cast-in-place piles of all sizes without excavation, as well as a set of a model range of universal pressing devices for shock-free and silent driving of driven piles (all sizes) and pile elements. This complex has already been used at important social facilities (Fig. 3.9).

The purpose of developing the complex is to provide technical support for the latest fast technologies for manufacturing foundations from shockless-pressed reinforced concrete and vibro-injected cast-in-place piles. Technical support should be aimed at increasing the reliability and load-bearing capacity of the currently used driven and driven piles, reducing the volume of excavation work while simultaneously compacting the soil (due to the installation of foundation wells without excavation), reducing the time and cost of manufacturing foundations.

Rice. 3.9. Reconstruction of the 2nd stage of the Mariinsky Theater in St. Petersburg

General characteristics of the complex:

♦ pressing devices are equipped with new geared inertial polyharmonic self-balancing vibrators, capable of creating pressing forces from tens to hundreds and even thousands of tons in a wide range of amplitudes and accelerations without shock and noise (i.e. without dynamic effects on the environment);

♦ The designs of universal loading devices allow them to be either freely suspended on the hook cages of cranes, or mounted on widely used pile driver installations with a lifting capacity of 3, 5, 10, 16 and 25 tf.

The first direction corresponds to a complete model range of a high-performance unified vibration-punching injection device for the production of reinforced concrete cast-in-place piles without excavation.

The proposed high-amplitude polyfrequency immersing devices, equipped with driving rotating mechanisms, protected from external influences from the soil being compacted, differ favorably from existing devices in that they are capable of producing foundation wells in a wide range of diameters and depths, as well as in load-bearing soils (without excavating the soil itself ) with significantly higher productivity and lower energy consumption.

The absence of oscillatory movements of the form-building body when pressing it into the ground eliminates compaction of the soil, which sharply reduces the drag of the soil and virtually eliminates the transfer of dynamic loads to nearby structures.

A unified range of high-performance vibration-pressing injection devices was created for the production of wells (without excavation) and reinforced concrete cast-in-place piles, for example, a high-performance, low-energy mounted device that is capable (without excavation) of providing: depth of wells (and piles) - up to 20 m; well diameters – 400, 530, 630, 820, 1020 and 1200 mm; manufacturing time for the well and pile – no more than 15 minutes; range of installed powers – from 30 to 120 kW; operating temperature range environment– from -25 °С to +40 °С. Energy source – AC mains voltage 380/220 V, 50 Hz. Physical service life is at least 10 years. Costs for materials during operation - on average no more than 10,000 rubles. per year. Vibration and noise background does not exceed environmental standards.

For driving pile elements, a significant and still widely used variety of devices (using geared inertial self-balanced vibrators as actuators) with impact (vibratory hammers), driving (vibratory hammers) and pressing (combined devices) actions are now known. Vibrating devices are proven and proven equipment.

In St. Petersburg, three types of piles are used depending on the engineering and geological conditions of the construction site (bedding, type and characteristics of soil):

♦ piles made with soil excavation;

♦ piles made with partial excavation of soil;

♦ compaction piles made without excavating soil as a result of its forced compression or displacement.

Method for constructing drilled injection piles using Gidrospetsstroy technology (micropiles)

The volume of use of drilled injection piles (micropiles) has grown tenfold over the past years. The experience of solving complex foundation building problems with their help has been significantly enriched. New technological schemes for constructing piles have been developed, new domestic and foreign equipment has been created, which has made it possible to radically change a number of technological operations and, on this basis, increase the load-bearing capacity of piles and sharply reduce the labor intensity of manufacturing.

“Recommendations for the use of micropiles” or the Service Station Organization Standard have been adopted as the Organization Standard of CJSC “PSU Gidrospetsstroy”.

The recommendations contain a classification of piles depending on their design and manufacturing technology, instructions on the field of application, a list of technological equipment and materials for the production of piles, as well as requirements for the calculation and design of foundations made of micropiles (bored injection piles).

The variety of designs and technologies for constructing drilled piles with a diameter of up to 35 cm made it possible to distinguish them into a separate class, called “micropiles” in the Recommendations by analogy with American and European standards.

Micropiles (micropile according to the classification Eurocode-7 and FHWA-SA -97-070 US) are a type of drilled and cast-in-place piles (according to the classification SNiP 2.02.03–85). They differ from traditional drilled piles in the following ways:

♦ small diameter (d = 150–350 mm);

♦ great flexibility (L/d = 60-120);

♦ trunk material (fine-grained concrete);

♦ manufacturing method (injection of concrete mixture into the well).

Micropiles, depending on the technology of their production used by the organization CJSC PSU Gidrospetsstroy, are divided into the following main types:

♦ BIS piles (drilled injection piles) - arranged by injecting a concrete mixture into a well without subsequent pressure testing;

♦ GSS piles (Gidrospetsstroy) - arranged with pressure testing of freshly laid concrete mixture with an additional portion of concrete mixture through a wellhead plug;

♦ PSSh piles - arranged by injecting a concrete mixture into a well through a column of “through sectional augers”;

♦ micro CFA (Continues Flight Auger) piles - arranged by injecting a concrete mixture into a well through a solid column of NPS (continuously moving augers);

♦ Geosmol piles (Russian analogue of Titan piles) - with a drill rod reinforced with wire packing.

Technological diagrams for constructing piles are shown in Fig. 3.10-3.12.

Rice. 3.10. Drilled injection piles, technological scheme of the GSS device:

I – drilling a well with a roller bit with flushing with a bentonite solution;

II – extraction of the drill string;

III – replacement of drilling mud with concrete mixture;

IV – immersion of the reinforced frame and pressure testing of the pile from the mouth.

1 – drill string with a roller bit;

2 – bentonite solution;

3 – injection pipe;

4 – reinforced frame

Rice. 3.11. Technological diagram of the installation of PSSh piles:

I – drilling a well using through sectional augers;

II – extraction of the drill string with simultaneous pressure testing of the well through the auger valve;

III – immersion of the reinforcement cage into the concrete mixture.

1 – through screw;

2 – screw valve;

3 – reinforced frame

Rice. 3.12. Technological diagram for installing micro CFA piles:

I – drilling a well by screwing in a drill string of NPS (continuously moving augers);

II – extraction without rotation of the drill string with simultaneous filling of the well through the auger valve;

III, IV – immersion of the reinforcement frame into the concrete mixture.

1 – NPS drill string;

2 – concrete mixture;

3 – reinforced frame

Steel tubular piles, open at the bottom

The use of steel tubular piles open at the bottom helps reduce the volume and time of construction activities, labor costs and pile material due to more rational functioning of the cross-section of the shaft under the design load.

Rice. 3.13. Using Tips

The use of tips (Fig. 3.13) allows you to expand the scope of application of pipe piles to larger diameters, to increased immersion depths, difficult soils and to more fully use the reserves of pipe piles in terms of their load-bearing capacity.

Method for constructing a package of bored piles

A package of bored piles is understood as a sequence of pile arrangement located in a geometric outline specified by a project, for example, linear, rectilinear, curvilinear, closed or open. The objective is achieved by the fact that in the method of constructing a package of bored piles by sequentially drilling a number of odd and a number of even secant holes for bored piles at a distance less than the diameter of the pile, followed by reinforcing the bored odd holes with frames made of reinforcement with a diameter 10 · 15% less than the diameter even column, and concreting. Initially, a number of wells are drilled, reinforced with frames, and on two diametrically opposite sides of each frame for odd-numbered wells, on the side facing the location of the adjacent even-numbered well, along the entire length of the frame, flexible reinforced sleeves made of airtight material are attached with temporary fastenings, plugged from below and having anti-adhesive coating. When concreting the pile, this coating is filled with gas or a mixture of gases to a pressure not less than the pressure of the hydrostatic column of the concrete mixture at the base of the pile, and is kept under pressure until the concrete hardens with the formation of grooves in it with an arc length in cross section of no more than half the perimeter of the reinforced sleeve, forming a section of elliptical or circular cylindrical surface along the length of the pile. After that, the gas is released from the hoses and they are extracted from the odd-numbered wells, then the even-numbered wells are drilled using the grooves formed in the odd-numbered piles as guides, they are reinforced and the even-numbered piles are concreted in them (Fig. 3.14). In this case, gas or a mixture of gases heated to a temperature exceeding the ambient temperature can be supplied into the reinforced hoses. Reinforced hoses of one reinforcement cage can be filled simultaneously, preferably by combining them with a tee with a gas source.

Rice. 3.14. Drilling even-numbered wells using grooves formed in odd-numbered piles as guides, reinforcing them and concreting even-numbered piles in them. Foreshaft 1 with guide holes for 2 odd and 3 even wells, 4 reinforcement frames, 5 flexible reinforced hoses

Method of constructing an injection pile

The method of constructing an injection pile (Fig. 3.15) involves constructing a well without extracting soil by pressing in the tip and injecting a hardening fixing solution through the injection pipe. What is new is that they use an injection pipe perforated along the entire length, at the end of which a conical tip is attached, consisting of a disk and cutting plates, the edges of which protrude beyond the base of the disk, the diameter of which is greater than the diameter of the injection pipe, and the injection pipe with a tip with simultaneous cutting of longitudinal grooves on the walls of the well and the formation of a gap between the walls of the formed well and the injection pipe, and at the end of the injection process, the injection pipe with the tip is left in the well. This increases the manufacturability and load-bearing capacity of the pile while reducing the time required for its construction.

Rice. 3.15. Method of constructing an injection pile:

1 – injection pipe;

2 – conical tip;

3 – cutting plates;

4 – through flanges;

5 – holes;

8 – compacted zone